1. Field of Invention
The present invention relates to a modified starch material of biocompatible hemostasis, biocompatible adhesion prevention, tissue healing promotion, absorbable surgical sealing and tissue bonding, and more particularly to a modified starch material, which is absorbable by human beings and animals, and applied directly to wound surface of humans and mammals, including wound surface with blood or extravasate, to stanch blood, prevent adhesion, promote tissue healing, seal section of wound tissue, prevent bleeding and exudation of tissue fluid, bond tissue and organ wounded by trauma or operation, help repairing tissue, and avoid or reduce surgical suture.
2. Description of Related Arts
Surgical operations and trauma may create bleeding wounds, which can produce a risk of excess blood loss. Therefore, hemostats to control bleeding should be applied in a timely manner. It is a common to apply biocompatible, absorbable hemostatic agents to bleeding wound sites to achieve hemostasis (cessation of bleeding) in surgical procedures, trauma treatment and home self rescue. There is clinical benefit to provide patients a hemostatic agent which is safe, efficacious, easy to use, and cost effective.
Prior absorbable hemostats consist of the following classes of materials:
Hemostatic sponge class: gelatin sponge, collagen sponge, chitosan sponge, carboxymethyl cellulose sponge, thrombin and fibrin sponges;
Hemostatic gauze/hemostatic film class: oxidized cellulose gauze, oxidized regenerated cellulose gauze, oxidized cellulose gauze with carboxymethyl cellulose;
Hemostatic glue class: fibrin glue, synthetic glue;
Polysaccharide hemostatic powder class: microporous polysaccharide powder, chitosan powder, algae powder.
A detailed analysis of absorbable hemostats in common use is stated below:
1. Absorbable Gelatin Sponges and Collagen Sponges:
The gelatin sponge is extracted from animal tissue, and the main component of the gelatin sponge is animal collagen. The gelatin sponge has a hydrophilic and multi-porous structure to concentrate blood components by absorbing water in the blood to arrest bleeding. However, gelatin is a collagen-based material from animal extract and contains heterogenetic protein which may cause anaphylaxis, resulting in feverish symptoms in patients. Further, the human body absorbs the gelatin material very slowly, and on average requires more than four weeks to fully dissolve. Foreign agents with slow absorption times can be sites for infection, tissue inflammation, and wound healing retardation.
Collagen sponges, which are also extracted from animal tissue, promote blood coagulation by activating the endogenous coagulation cascade while also concentrating blood components by absorbing water in the blood.
Like the gelatin sponges, collagen sponges are also sourced from animal collagen and contain heterogenetic protein, which is slow to absorb in the human body. The collagen sponge may produce complications of anaphylaxis, slow healing and infections. Due to these clinical risks, applications of collagen sponges may be limited in the future.
2. Oxidized Cellulose Hemostatic Gauze and Oxidized Regenerated Cellulose Hemostatic Gauze:
Oxidized cellulose is a cellulose derivative. The hemostatic mechanism of oxidized cellulose is the concentration of blood components through the hygroscopic activity of oxidized cellulose, which stimulates blood coagulation as the carboxyl material combines with haemoglobin Fe to produce acidic hematin in the blood. The resulting brown gel seals capillary vessels and promotes hemostasis. Oxidized regenerated cellulose has the same mode of action as oxidized cellulose.
Oxidized cellulose is synthetic. Normal human tissue degrades oxidized cellulose slowly by metabolizing enzymes. This process generally require 3-6 weeks depending on the dosage and the tissue location in the body. Oxidized cellulose may cause local infection and adversely affect local tissue healing. Patent application, China publication number CN1533751A, discloses a hemostatic wound dressing with a trade name of SURGICEL. SURGICEL includes a cellulose fabric and a multi-porous polymer substrate on the fabric surface which contacts the wound. The substrate contains biocompatible, water-soluble polymers. The fabric fibers are oxidized regenerated cellulose and the biocompatible, water-soluble polymers are polysaccharides. This hemostatic wound dressing consists primarily of oxidized cellulose, a slowly absorbing material in the human body.
3. Fibrin Glues:
Fibrin glues consist of fibrinogen, thrombin, aprotinin and calcium chloride. The hemostatic action relies mainly on the activation of fibrinogen by the thrombin to promote coagulation cascade. Fibrin sealants are a mixture of fibrinogen and thrombin and have been widely used in recent years. The thrombin and fibrin in fibrin glues are sourced from either animal or human blood components and therefore create the risk of anaphylaxis and viral infections such as hepatitis, AIDS, and BSE. Fibrin glues demonstrate weak adhesion when applied to wet, bleeding tissue and may be ineffective in the presence of active bleeding. Further, fibrin glues require special mixing, timing and storage condition.
4. Natural Biological Polysaccharide Products:
In recent years, natural, biological polysaccharide-based products have focused much attention. The natural biological polysaccharide products are derived from plant material and chitosans and usually presented in powder form. These products have good biocompatibility, no toxicity, no tissue irritation, and no risk of anaphylaxis or viral infection from animal or human components contained in other hemostats.
Chitosan/Chitin Products:
Chitosan products are typically available in high swelling and non-absorbable sponges. Chitosan is made from the crushed shells of crustaceans. Chitosan has rapid hydrophilic capability and can activate the blood coagulation mechanism through its strong ionic charge. However, due to a lack of human enzymes to degrade chitosan, chitosan-derived products will be confined to topical applications. There is no evidence that chitosan products have been used in clinic as absorbable surgical hemostats.
Microporous Polysaccharide Hemospheres (MPH):
In 2002, MEDAFOR, INC. in the USA developed an absorbable hemostatic material called Arista™ (U.S. Pat. No. 6,060,461), which consists of microporous polysaccharide particles (MPH). The microporous polysaccharide particles are made through the reaction of purified starch and epichlorohydrin, wherein the epichlorohydrin reacts with starch molecules. This reaction results in the formation of ethyl propanetriol which creates a glucose molecule crosslink to the 3D network structure.
There are a few disadvantages of the MPH hemostatic powder. Firstly, the delivery of MPH mainly focuses on local, easy-to-access wound sites but presents some difficulties for effective applications for deep, tortuous wounds, in particular the endoscopic procedures (such as minimally invasive surgery via endoscope and laparoscope). Secondly, during the production process, epichlorohydrin, a colourless, oily and toxic chemical, is employed to produce a required reaction. This production process is not environment friendly. The cost of production is relatively expensive. Thirdly, the hemostatic efficacy of MPH is not satisfactory in particular for profuse bleeding, due to its low hydrophilic capacity and slow water absorption characteristic. Fourthly, the adhesiveness of the MPH to tissue is low following contacting with blood. The low viscosity, low adhesiveness of MPH following water absorption may reduce the hemostatic efficacy of MPH due to its weak sealing capability to wounded tissues and broken vessels. Fifthly, in the presence of active bleeding, the MPH powder can be easily washed away by blood flow if not compressed with a gauze on the top of powder. This gauze compression requirement adds an additional step in the hemostatic powder application technique and may risk re-bleeding when the gauze is removed. Therefore, MPH may have an unsatisfactory hemostatic efficacy for active bleeding.